1. Field of the Invention
The present invention relates to a memory control device for a bioassay apparatus and, more particularly, to a memory control device for an embedded microcontroller of a bioassay apparatus for allowing convenient changes to stored programs for controlling a robotic arm associated with the embedded controller.
An example of an automated blood/plasma sampling system for which the present invention is applicable is disclosed, for example, in U.S. patent application Ser. No. 07/833,951 to Hulette et al., filed Feb. 11, 1992, which is a continuation-in-part application of U.S. patent application Ser. No. 07/443,951, filed Dec. 1, 1989, now abandoned. The subject matter of the continuation-in-part application to Hulette et al. is incorporated herein by reference. An example of a piercing and sampling probe is disclosed in U.S. patent application Ser. No. 07/874,371 filed Apr. 27, 1992, by Moreno. The subject matter of the application to Moreno is incorporated herein by reference. Another example of a sampling probe is disclosed in U.S. Pat. No. 5,178,019, issued Jan. 12, 1993, to Keiter. The subject matter of the patent to Keiter is incorporated by reference herein. An example of a liquid level sensor and control circuit for sensing a position of a probe with respect to a surface of a liquid in a container is disclosed in a U.S. patent application Ser. No. 08/088,656, to Ramey et al. filed concurrently with the present application. The subject matter of the application to Ramey et al. is incorporated by reference herein. The subject matter of the applications to Hulette et al., to Moreno and to Ramey et al., and the patent to Keiter are each assigned to the same assignee as that of the present application.
2. Description of the Related Art
Automated sample handling systems are known which automatically dispense fluid samples, such as blood plasma and reagents, into a reaction well of a cuvette. Such instruments are useful in the field of biochemical analysis for measuring blood clotting times and for automatically carrying out other bioassays. Additionally, these instruments are useful in the field of chemical assays for automatically carrying out chemical assays. An example of an automated sample handling system for carrying out blood and plasma bioassays is described in U.S. patent application Ser. No. 07/443,951 to Hulette et al.
In this particular system, fluid samples, such as blood or plasma, are stored in containers, such as test tubes, which are vacuum sealed by way of a rubber septum that must be pierced in order to withdraw a measured amount of the sample for testing purposes. U.S. patent application Ser. No. 07/874,371 to Moreno, incorporated herein by reference, discloses an example of a piercing and sampling probe suitable for piercing and sampling a measured amount of liquid.
The Hulette et al. system also includes a temperature controlled housing provided for storing fluid samples and reagents at a relatively cool temperature for preventing degradation of the samples and reagents prior to sample analysis. The temperature controlled housing typically maintains the fluid samples and reagents at a temperature of 10.degree. C. The actual analyses are generally carried out at 37.degree. C. (98.6.degree. F.), standard human body temperature. Accordingly, it is necessary to heat the fluid sample and reagents to 37.degree. C. prior to analysis. U.S. Pat. No. 5,179,019 to Keiter, incorporated herein by reference, discloses a sample probe device useful for heating fluid samples and reagents prior to analysis.
The piercing and sampling probes in the Hulette et al. system are raised and lowered in operation by a robotic arm under control of an embedded controller which maneuvers a sample probe between reagent containers and a reaction cuvette for automatically aspirating and dispensing reagents. The embedded controller is responsive to a sensor circuit for detecting the surface of a liquid, whether a sample or reagent, for accurately controlling movement of the probe. Details of a sensor circuit for detecting the surface of a liquid are disclosed in the application to Ramey et al. Ser. No. 08/088,656.
Specific maneuvering of the robotic arm for positioning the probe may vary depending on the particular bioassay effected by the automatic sampling system. Examples of variations could be a particular sequence of probe positions, sample temperature or sample heating time, and sample volume. Consequently, program instructions executed by the embedded controller may also vary from particular bioassay to bioassay. In some cases, variations in bioassay operations require customization or empirical determination.
Thus, for embedded controllers in an automated blood/plasma sampling system such as the one disclosed by Hulette et al., it is advantageous to alter program instructions stored in a program memory associated with the embedded controller without physically accessing and replacing the program memory. This allows program instructions executed by the embedded controller to be conveniently changed by downloading a program file from a host computer, saving the time and effort normally associated with removing program memory of the embedded controller from the instrument for replacement. It is also advantageously possible to remotely update the firmware from a centrally located main computer system through a modem or network connection.